The present invention relates broadly to a device for indicating the rotational position of a rotary shaft, and more particularly, to a rotary shaft position indicator and control for use in harsh environmental conditions.
The present invention is particularly applicable to fluid and other flow systems in which it is desirable to monitor the condition of rotary valves (i.e. open or closed) and/or to control the opening or closing of successive valves in the flow line as a function of the open or closed state of the preceeding valves. Typically, in the prior art, electrical switches that are mechanically actuated in response to the operative state of the rotary valve have been utilized. These mechanically actuated switches are frequently subjected to severe environmental conditions to include dust, moisture, or other corrosive or explosive foreign matter. Such adverse environmental conditions have a deleterious effect on the electrical switches, and over a period of time may lead to switch malfunctions causing erroneous indicator and control signals. If, for example, a switch fails to generate and "open" or "closed" signal to a successive valve in a fluid flow system, it can be readily appreciated that serious consequences to the system operation may develop.
The present invention solves the problems associated with the prior art systems in that it provides a rotary shaft position indicator and control in which an electrical switch is enclosed within a housing that is sealed against the introduction of the above-mentioned deleterious matter. The switches are actuated utilizing a magnetic coupling through a non-magnetic wall of the housing. Thus, rotary shaft position indicator and control signals are generated utilizing switches which remain unaffected by the harsh environmental conditions that may exist in particular system applications.